Fifty years ago the world got its first taste of James Bond on the silver screen. Based on the series of spy novels by Ian Fleming, Sean Connery made his debut as Agent 007 in 1962 with Dr. No. Last year the 23rd film in the series hit theaters: Skyfall, released to coincide with the 50th anniversary of the release of Dr. No. After six Bonds, three Ms, four Moneypennys, three Qs, seven Felix Leiters, and countless gadgets, bad guys, henchmen, beautiful women, and vodka martinis (shaken, not stirred), the longest-running film series ever is still going – and, judging by the finale of Skyfall, can perhaps be expected to run for another fifty years.

(Note: the following contains minor spoilers for On Her Majesty's Secret Service and Skyfall.)

Connery is the original Bond, and for many fans, the greatest. He set the standard for 007, jetting about saving the world like it's nothing, bedding many beautiful women in the process. Connery's Bond is a rogueish chap who got the job done, thinking nothing of using one of his several curvaceous bedmates as a shield to block bullets, punches, or anything else thrown at him (assuming, of course, she was working for the competition). Nothing slips by Bond; he takes care of the problem no matter what.

Connery portrayed Bond for the first six films of the series, being replaced by George Lazenby in 1969's On Her Majesty's Secret Service – a lame and silly outing barely carried by pretty boy Lazenby. He can't hold a candle to Connery's lascivious ways, although he tries – he is even given a resort-full of brainwashed women, which he takes advantage of, almost more because he is expected to. Lazenby thankfully decided during filming that he didn't enjoy the role – which is obvious – and opted out of future films, turning it back over to Connery one last time (not counting Never Say Never Again) for Diamonds Are Forever.

Roger Moore took up the mantle with a bang for the first time in 1973's Live and Let Die. Moore takes to the role quickly and naturally, with the help of ridiculously entertaining adversaries. He takes on seemingly all of Harlem in his first film, followed immediately in the next by a three-nippled Christopher Lee and his midget sidekick in The Man With the Golden Gun. Before long he is fighting Richard Kiel in space and Christopher Walken on top of the Golden Gate Bridge. Moore's Bond is not as blatantly misogynist as Connery; he is more suave, more refined – he respects the women he beds and he goes about his missions in a more professional manner, coming across more as an effective spy who knows his job rather than a rambunctious Scotsman in it for the sexual rewards.

Moore was followed by Timothy Dalton, who only lasted for two films: The Living Daylights and License to Kill. Dalton is something of a departure from the Bond formula we have become accustomed to; he is darker, more serious. Hardly a quip or a smile escape his lips, and though we surmise that he enjoys his women, the only hint of the intense sexuality of the previous Bonds is at the beginning of The Living Daylights when he happens to drop in on a private boat carrying a bored lady yearning for “a real man.” Dalton is an excellent Bond, and it would have been interesting to see how he would have evolved had he continued beyond merely two films.

My generation grew up the next-to-last portrayal: Pierce Brosnan, whose films finally seem to push the series firmly into the modern age, with MI6 fully revamped and Judi Dench taking the role of M. Brosnan is perhaps the quintessential 007; a mix of serious and playful, of caring and merely horny, the best word to describe Brosnan's Bond is debonair. Of course, these films end up rather ridiculously; while the gadgetry and evil plots have always tended towards the fantastical, Brosnan's final film, Die Another Day, pushes things firmly into the realm of science fiction, what with invisible cars and gigantic sun-lasers and the like.

Everything is brought back down-to-earth with the reboot: Casino Royale, starring Daniel Craig as Agent 007. He is perhaps the most badass Bond, taking the best bits of Brosnan and Dalton and making the character entirely his own. He is suave like Brosnan, but with the seriousness and dedication of Dalton. His three films also focus more on his relationship with M – still portrayed by Judi Dench, who becomes perhaps one of the most interesting characters in the whole series, culminating in Skyfall, which is really as much about her as it is about Bond.

So: who is James Bond? There are six portrayals, and there has been much speculation as to the nature of the character. Are all the actors meant to portray the same person? Or is “James Bond” merely the code name which corresponds with the 007 designation? This is a secret spy agency after all, and false identities are part of the game. It has been presumed that each different actor is, in fact, a different “James Bond,” and that perhaps with each change of actor the previous agent had died in duty (or perhaps retired – Never Say Never Again is non-canon, but perhaps some hints can be gleaned from it anyway).

However, they seem to be the same character – for the most part. The first change of Bond, as mentioned, occurs with Lazenby. The opening scene of On Her Majesty's Secret Service features a typical chase and fight scene, at the end of which the girl jumps in her car and speeds away. Lazenby's Bond merely smiles and remarks, “This never would have happened to the other fellow,” meaning, presumably, Connery. This film is key, though, as at the end Bond marries the film's love interest – and she is promptly killed.

It is this fact that ties together the rest of the Bonds up through Brosnan. In The Spy Who Loved Me, Russian Agent XXX shares her knowledge of Bond, including the fact that he was once married and she died. Also, in the beginning of For Your Eyes Only, he visits the grave of his wife. In License to Kill, Bond's friend Felix Leiter remarks to his new bride that he was once married. In The World is Not Enough, Brosnan's Bond is asked if he has ever lost someone special, to which he doesn't respond, but gives a silent and significant look.

How is it possible, however, for Bond to have a career spanning four decades and not age? The other characters grow old. M is replaced twice, and Desmond Llewelyn's Q speaks of retirement and introduces his replacement in The World is Not Enough. Miss Moneypenny is a mystery, however. Lois Maxwell plays her up until A View to a Kill, in which she even remarks upon her old age. In the next film, The Living Daylights, she is suddenly replaced by the young and perky Caroline Bliss, who only lasts for the extent of the Dalton films before being played by Samantha Bond for the Brosnan films. Is “Miss Moneypenny” perhaps a code name as well?

And what of Felix Leiter, Bond's CIA friend? He is played by a different actor in almost every film in which he appears. We can feel pretty sure that “Felix Leiter” is a real name, not a code name, and yet he likewise doesn't appear to age.

There are some hints given in the Daniel Craig films, specifically Skyfall – however, it is with him that the series was rebooted, so it must be decided whether we can apply this information to the preceding films. In Skyfall, Bond returns to his childhood home, where he looks at the graves of his parents – last name, Bond, thus, a given name, not a secret identity. The character Eve, as she settles down at the end at her new post as M's secretary, introduces herself more completely as Eve Moneypenny – again, a real name.

Assume “James Bond” is a code name – in which case we can perhaps treat Casino Royale as a continuation of the series, merely disguised as a reboot. After all, Judi Dench remains as M, which is curious. Here, we witness an agent being given the designation of 007 – perhaps replacing Brosnan's Bond (killed in the field)? However, there is the aforementioned issue of the graves of Bond's parents.

Perhaps the answer lies in the realm of the truly fantastic. After all, this is the world of insanely advanced technology, even back in the sixties. Could it be possible that each new 007 has his brain wiped and replaced with the basic memories and personality of his predecessors? Thus ensuring the continuation of James Bond, the best agent in the field. Remember when Lazenby as Bond encounters Blofeld in On Her Majesty's Secret Service – he did not recognize him, despite being quite familiar with Connery-as-Bond. This explanation is far-fetched – but not as much as, say, the “DNA Therapy” presented in Die Another Day.

Assuming this is the case, we look again at the Daniel Craig films. Throughout the series, the setting of MI6 evolved with the times, growing in scope and scale up til it is blown up in Skyfall. They are forced to relocate, and in the final scene, we are, as mentioned, introduced to Moneypenny, at which point we recognize the room in which she has her desk, the signature hat rack, the padded door to M's office, which is also set up as in the original films.

The series is perhaps a mobius strip; we return to the beginning at the end of the first half-century run, but everything has been turned on its head, so it is simultaneously a new beginning while returning to the original start.

However, this still doesn't account for the mystery of Miss Moneypenny and Felix Leiter (who even switches race in the Craig films). Also, M's timeline doesn't add up. Assuming Goldeneye takes place in the mid-nineties, when it was made, this marks the start of Judi Dench as the new M, whereas in Skyfall, Silva remarks that he began as an agent in 1986, when Dench was M.

There is no clear answer. Perhaps the reboot is just a reboot. Perhaps the world of 007 is a place devoid of logic and continuity not meant to be questioned.